1. Field of the Invention
This invention relates to an apparatus for mixing gas and liquid phases, and more particularly, to an apparatus for mixing pressurized air with pressurized waste liquor at the inlet of a wet oxidation system heat exchanger device.
2. Description of Related Art
In the continuous flow wet oxidation of aqueous waste liquors, the general practice is to pressurize the waste liquor and combine it with a pressurized oxygen-containing gas, such as air, to give a pressurized gas/liquor mixture. The mixture is then heated to a selected temperature for a certain time period in a pressure vessel to effect wet oxidation treatment. Heat energy is recovered in a process heat exchanger where the raw gas/liquor mixture is heated by the hot oxidation mixture exiting from the pressure vessel. Compared to liquor alone the gas/liquor mixture provides improved heat transfer in the tube and shell heat exchangers commonly employed in continuous flow wet oxidation systems.
Huesler et al. in U.S. Pat. No. 2,932,613 disclose pumping liquor through a first heat exchanger, the adding compressed air to the liquor, with this mixture flowing on to additional heat exchangers in the wet oxidation system. No details of the apparatus for performing this air addition are provided.
In U.S. Pat. No. 3,907,678 Pradt et al. disclose adding air before and after a heat exchanger to prevent polymerization of wastewater components in the wet oxidation system. Again, no details of the apparatus for performing this air addition are provided.
Bauer et al. in U.S. Pat. No. 4,384,959 describe adding inert dilution gas a various points to a pure oxygen wet oxidation system. Likewise, no details of the apparatus for performing this gas addition are provided.
In wet oxidation treatment, certain waste liquors mixed with oxygen-containing gas, such as air, are prone to form viscous solids in the piping prior to the mixture entering the system's heat exchanger. These solids can plug the inlet piping and shut down the continuous flow system. The waste liquor is stable in the absence of oxygen (air), even when heated to the boiling point, about 100.degree. C.
To overcome this operational problem, applicants have invented an air/liquor mixing apparatus which introduces the pressurized air into the pressurized waste liquor at the entrance to the heat exchanger, such that the liquor has been heated to an elevated temperature before contacting the oxygen in the air. No additional preheating device for the liquor is required. The mixing apparatus attaches to the tube inlet of a tube and shell heat exchanger, is easily disassembled for inspection and cleaning, and can be designed to provide air delivery at a selected position relative to the inlet point of waste liquor.